Compartmentalized reservoir shows oil in place and location of horizontal wells to maximize production and recovery. (All graphics courtesy of Schlumber)

Oilexco Inc. is a small independent Canadian energy company headquartered in Calgary. It entered the North Sea in 2002 with the award of three lease blocks in the 20th UK Offshore Licensing Round. This licensing round was part of a UK fallow fields initiative, designed to attract new operators with fresh perspectives and stimulate the reappraisal of mature North Sea acreage. Today, all of the Oilexco E&P activity is located in the UK Central North Sea.

In 2003, Oilexco had a major success in its first North Sea exploration project in the Brenda field, 75 miles (120 km) northeast of Aberdeen in Block 15/25b. The Brenda field is a complex stratigraphic trap, producing oil from a system of thin channelized turbidite sandstones. Oil from Brenda is 40º API, which trades at a premium to the Brent Standard.

After its first discovery in the Brenda field in 2003, Oilexco quickly began an extensive appraisal program, managed from its Calgary headquarters, utilizing well and test data and models derived from two 3-D seismic surveys covering the area. The company had a small internal group of field development staff and no previous North Sea experience, so consultants were hired to augment the project team.

The consultants were knowledgeable, but managing the data and the project proved to be a challenge. In addition, Oilexco considered the reserves estimates derived from the initial geological models to be too conservative. Unless reserves estimates could be confidently increased, justifying the investment required to move the project forward to development would be difficult.
Oilexco selected Petrel seismic-to-simulation software to take control of the workflow process, manage and share data, and coordinate between the consultants and the internal members of the multidisciplinary team to develop a more accurate reservoir model.

The specific challenge with the geologic model was accurately defining the oil water contacts (OWC). Exploration data showed variation in the depths of OWC for different areas of the reservoir as a result of the stratigraphic complexity. It was thought that consultant models did not account for this variation and complexity, which resulted in overly conservative models.

The implemented fault modeling workflow enabled Oilexco to accurately model the OWC changes within the reservoir based on well data. A new geological model was generated, characterized by polygon-shaped zones, which accurately reflected the variability of OWCs across the Brenda reservoir.

Schlumberger well placement engineers worked with the Oilexco operations geology team to plan the horizontal development wells and optimize wellbore positioning. Well planning and positioning used a combination of software and wireline and drilling technology, including real-time logging- (LWD) and imaging-while-drilling information. A bed boundary mapping technology was successfully used to keep the wellbore trajectory optimally located within the reservoir sand and avoid the underlying aquifer.

This mapping technology determined distances to formation boundaries such as top reservoir and OWC and measured formation resistivity and orientation in real-time. These real-time drilling data were quickly imported into the geologic model. Advanced analysis and interpretation features, including the ability to resolve uncertainties in seismic data, enabled integration of all available information to develop an increasingly accurate reservoir model.

The solution enabled improved data sharing, workflow and communication throughout the planning and operations phases of the development project. It eliminated the gaps in traditional systems that require handoffs from one technical domain to the next and captured knowledge and best practices for the future.

Although a highly sophisticated tool, the model is user-friendly, and members of the Oilexco development team were able to work independently through much of the workflow and functionality, aided by technical and application support from experienced consultants on the team.

Oilexco realized the value of the Petrel integrated interpretation and modeling workflows for the geophysics, petrophysics, geology, and engineering work processes. The application platform enabled collaboration between the Oilexco geology and geophysics team and external consultants, maximizing its business plans and increasing investment value. It also allowed for more reservoirs to be interpreted and characterized by fewer people.

Two geologists managed eight pools, typically the work of five to ten people. Oilexco reports that the implementation of the software prevented the need to add three or more in-house geoscientists to produce the same results. The software tools, real-time drilling data and technology, and workflow enabled the company to scrutinize the data and analyze the reservoir in greater detail, resulting in deeper understanding and more accurate results.

Oilexco reported significant improvement in the quality of its reservoir model and confirmed the reserves in Brenda were sufficient to move the project forward to development.